The disclosure of Japanese Patent Application No. 2001-75614 filed on Mar. 16, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to an air cleaner and an adsorption filter for an internal combustion engine. More particularly, the invention relates to an air cleaner and an adsorption filter for an internal combustion engine which are capable of preventing an air cleaner element from being damaged by a backfire of the engine and preventing fuel vapor leaking via an intake system from diffusing into external air.
2. Description of Related Art
Motor vehicle engines are equipped with an air cleaner for filtering external air. In recent years, there is provided an air cleaner having an adsorbent for preventing fuel vapor leakage via an intake system from flowing out into the atmosphere.
As a measure for disposing an adsorbent for adsorbing fuel vapor leaking via an intake system, an arrangement has been proposed in which a sheet formed by sandwiching an adsorbent between two layers of filter paper or non-woven fabric is fixed in an air cleaner (Japanese Utility Model Laid-open Application No. 60-14269).
However, such a known arrangement has drawbacks because a normal air cleaner element and an adsorbent-equipped element are disposed in parallel. Firstly, there is a danger of fuel vapor leaking out into the atmosphere through the normal element. Secondly, the filter paper or non-woven fabric of the adsorbent-equipped element becomes easily clogged with dust, so that the air-flow resistance of the adsorbent-equipped element considerably increases and the fuel vapor adsorbing performance considerably deteriorates.
Furthermore, since the filter paper or non-woven fabric is poor in heat resistance, the filter paper or non-woven fabric of the adsorbent-equipped element is easily damaged by backfire, so that activated carbon or the like may fall out of the adsorbent-equipped element.
It is an object of the invention to provide an air cleaner and an adsorption filter for an internal combustion engine which are capable of reliably blocking leakage of fuel vapor into the atmosphere and preventing the clogging thereof with dust and damage thereto caused by backfire.
A first aspect of the invention is an air cleaner for an internal combustion engine which includes a housing that has an intake air inlet for introducing an external air and an intake air outlet for supplying an intake air to the internal combustion engine, an air cleaner element disposed within the housing for filtering the external air introduced, and adsorption means disposed at an internal combustion engine side of the air cleaner element for adsorbing a fuel vapor. The adsorption means includes a particulate activated carbon, a heat-resistant mesh member for holding the particulate activated carbon, and a non-woven fabric.
According to the first aspect of the invention, when the intake manifold has a negative pressure due to operation of the engine, air is drawn into the engine sequentially via the air cleaner element and the adsorption means in that order.
If a normal woven fabric, which is formed basically by arranging warp yarns and weft yarns in a two-dimensional fashion, is used in an air cleaner, it is necessary to expand the gap between yarns in order to enhance the air permeability. Therefore, if such a woven fabric is used to hold the particulate activated carbon, it becomes difficult to effectively prevent the particulate activated carbon from falling off.
In contrast, a non-woven fabric is formed by entangling fiber in a complicated and random fashion. Therefore, the non-woven fabric has an excellent capability of holding or trapping fine powder, and therefore can effectively prevent activated carbon powder from falling off.
Furthermore, air passes through the non-woven fabric after dust has been removed from the air by the filter element. Therefore, the clogging of the non-woven fabric is more effectively prevented.
While the engine is stopped, air is not introduced, so that fuel vapor evaporated from deposits of fuel inside the engine enters the internal combustion engine air cleaner. However, the fuel vapor adsorbs to the particulate activated carbon of the adsorption means, and is therefore substantially prevented from escaping into the atmosphere.
Furthermore, if the internal combustion engine backfires, the heat-resistant mesh member blocks passage of fire, thereby preventing damage to the non-woven fabric and damage to the air cleaner element.
In the internal combustion engine air cleaner of the first aspect of the invention, the non-woven fabric may have a percentage of void of at least 90%. As the percentage of void of the non-woven fabric is set at 90% or higher, increase in pressure loss can be curbed, and the clogging can be prevented.
In the internal combustion engine air cleaner of the first aspect of the invention, the heat-resistant mesh member may have a mesh size that is smaller than a particle size of the particulate activated carbon. As the mesh size of the heat-resistant mesh member is set smaller than the particle size of the particulate activated carbon, the particulate activated carbon can be reliably held by the heat-resistant mesh member.
In the internal combustion engine air cleaner of the first aspect of the invention, it is possible that the non-woven fabric has been processed for a flame retardancy. The non-woven fabric processed for flame retardancy will prevent damages thereto even if the mesh member should fail to block passage of fire or the mesh member should have a damage.
In the internal combustion engine air cleaner of the first aspect of the invention, the non-woven fabric may be formed by a flame retardant fiber. The non-woven fabric formed by a flame retardant fiber will prevent damage thereto even if the mesh member should fail to block passage of fire or the mesh member should have damage.
In the internal combustion engine air cleaner of the first aspect of the invention, the non-woven fabric may be formed by an activated carbon fiber. As the non-woven fabric is formed by an activated carbon fiber, the activated carbon fiber also adsorbs fuel vapor, thereby further enhancing the adsorption capability of the adsorption means.
A second aspect of the invention is an adsorption filter for use in an internal combustion engine air cleaner which has a housing that has an intake air inlet for introducing an external air and an intake air outlet for supplying an intake air to the internal combustion engine, and an air cleaner element disposed within the housing for filtering the external air introduced, and which is disposed at an internal combustion engine side of the air cleaner element. The adsorption filter includes a particulate activated carbon, a heat-resistant mesh member for holding the particulate activated carbon, and a non-woven fabric.
The adsorption filter of the second aspect of the invention can be used by disposing it at the internal combustion engine side of the air cleaner element. In this case, the adsorption filter achieves substantially the same advantages as those of the first aspect of the invention.